Here are some notes from my presentation in class:

Smoothing a noisy signal with an ‘integrator’:

float smoothedSignal = 0; // Declared as a global variable
 
void loop(){
  float A = 0.9;
  float B = 1.0-A;
 
  float noisySignal = mouseY; // ... or something
  smoothedSignal = A*smoothedSignal + B*noisySignal;
}

Non-linear transformations of signals:
See the “ShapeTween” Processing library by Lee Byron and myself, or have a look at the following pages:
http://www.flong.com/texts/code/shapers_poly/
http://www.flong.com/texts/code/shapers_exp/
http://www.flong.com/texts/code/shapers_circ/
http://www.flong.com/texts/code/shapers_bez/